1. Technical Field
The present invention relates to image sensor packaging structures and manufacturing methods thereof. More particularly, the present invention discloses a molded image sensor packaging structure having a lens module with a predetermined focal length and a manufacturing method thereof.
2. Description of Related Art
Image sensors have been widely used in various digital image products as a component that receives light and converts optical signals into electrical signals. With the popularization of diverse digital image products, the demand for image sensors is increasingly growing. Thus, for meeting the requirements of simplifying the packaging process of electronic products and downsizing the packaging structure of image sensors, the manufacturers have all spent efforts to make improvements in the packaging process and packaging structure.
Packaging is provided for preventing the image sensor module form being damaged by external force or environmental factors, and for providing electrical connection between the image sensor module and the exterior environment, so as to secure transmission of signals therebetween.
However, the existing packaging structures still have challenges to be overcome, for example:
1. The problem related to space: in the existing COB (Chip On Board) packaging approach, a relatively large space is required for accommodating metal leading wires. In addition, since the conventional COB packaging approach is accomplished by adhering an image sensing chip on a substrate or circuit board, the overall height is increased by the thickness of the substrate or circuit board and hard to be reduced. In order to solve the problem that wiring consumes space in COB packaging, chip-size packaging plus wafer-level optics (CSP+WLO) has been used with a lens module. However, in such an approach, an additional piece of optical glass has to be set between the image sensing chip and the wafer-level optics, so the overall height is subject to the required focal length and hard to be reduced. Moreover, COB packaging needs additional substrates or circuit boards. However, because of the shortage and the consequent price hike of the global resources, the manufacturing cost would be increased.
2. The problem related to lateral leakage: the existing packaging methods are all subject to lateral leakage and need additional lens hoods or lateral light-blocking coating. The additional lens hoods and coating can not only increase material costs but also complicate the manufacturing process.
3. The need of focusing: in the traditional packaging process, a focusing mechanism is required for focusing, so as to achieve the optical definition. This work needs special devices and processes, and thus causes increased costs.
4. Leakage of the molding compound over the upper surface of the lens module: in molding and packaging processes, since the mold and the lens module are both made of rigid materials, when the upper mold member of the mold directly presses upon the lens module, the lens module is likely to be damaged under compression, thus reducing the yield of the image sensor packaging structure. Furthermore, since tiny gaps exist between the upper mold member and the upper surface of the lens module, when a molding compound is filled into the mold cavity, the molding compound tends to leak over the upper surface of the lens module under capillarity, thereby adversely affecting the image sensing effect of the image sensor packaging structure.